A Role for Caveolin in Transport of Cholesterol from Endoplasmic Reticulum to Plasma Membrane

doi:10.1074/jbc.271.46.29427

A Role for Caveolin in Transport of Cholesterol from Endoplasmic Reticulum to Plasma Membrane*

From the Department of Cell Biology and Neuroscience, University of Texas Southwestern Medical Center, Dallas, Texas 75235-9039

^‡To whom correspondence should be addressed.

Abstract

Caveolin is a 22-kDa membrane protein found associated with a coat material decorating the inner membrane surface of caveolae. A remarkable feature of this protein is its ability to migrate from caveolae directly to the endoplasmic reticulum (ER) when membrane cholesterol is oxidized. We now present evidence caveolin is involved in transporting newly synthesized cholesterol from the ER directly to caveolae. MA104 cells and normal human fibroblasts transported new cholesterol to caveolae with a half-time of ∼10 min. The cholesterol then rapidly flowed from caveolae to non-caveolae membrane. Cholesterol moved out of caveolae even when the supply of fresh cholesterol from the ER was interrupted. Treatment of cells with 10 μg/ml progesterone blocked cholesterol movement from ER to caveolae. Simultaneously, caveolin accumulated in the lumen of the ER, suggesting cholesterol transport is linked to caveolin movement. Caveolae fractions from cells expressing caveolin were enriched in cholesterol 3-4-fold, while the same fractions from cells lacking caveolin were not enriched. Cholesterol transport to the cell surface was nearly 4 times more rapid in cells expressing caveolin than in matched cells lacking caveolin.

Footnotes

↵* This work was supported by National Institutes of Health Grants HL 20948, GM 43169, and GM 15631 and by the Perot Family Foundation. The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵¹ The abbreviations used are:

ER

endoplasmic reticulum

DMEM

Dulbecco's modified Eagle's medium

PBS

phosphate-buffered saline

BSA

bovine serum albumin

GPI

glycosylphosphatidylinositol

MES

4-morpholineethanesulfonic acid

Tricine

N-[2-hydroxy-1,1-bis(hydroxymethyl)ethyl]glycine.
↵²B. L. Trigatti, R. G. W. Anderson, and G. E. Gerber, submitted for publication.
- Received June 28, 1996.
- Revision received August 23, 1996.